Hi Paul - You make a persuasive argument.Dear Skippy, those (clearly, synthetic) oils are entirely inappropriate to this engine when using AVGAS. In fact, they are deadly. Only the base mineral oil is able to suspend the lead compounds in cylinder blowby, synthetics drop it out of suspension in ways that block oil galleries. The typical oil used is a 100 or 120 monograde ashless dispersant, corresponding to SAE 50 and SAE 60. Detergent oils are completely out of the question. In point of fact, they are OBSOLETE in aviation oils mainly due to the hazards they create. Multigrade aviation oils are available too - for a number of reasons, they are not as popular as you might think they should be. In certain parts of this engine, oil can reach rather high temperatures (notably in the rocker box on the exhaust valve side), resulting in oxidation and sludge formation, but there is also the sludge produced from blowby lead products to consider. These high temperatures can result in degradation of the viscosity modifiers used to maintain viscosity at higher temperatures in multi-grade oils - dependent on individual installations and operations, in many cases it never happens at all. Gasoline oil dilution and/or pre-heat allows mono-grade oils to be used in cold environments. Please do consider whether or not your automotive tribology knowledge actually crosses over to aviation engines - in many cases, it is most inappriopriate.
I don't doubt your statement but I would question; why on earth owner/mechanics are sticking with such ancient oil technology, when more efficient alternatives exist.You can be a doubter, but doubt has little influence on the aviation world's reality. Lycoming and Continental aviation oils, are mostly single-weight, and even the multiweight oils are being run in engines that were designed to run single-weight. Lyc oils are typically 50 weight. Consider a positive displacement oil pump (they all are) trying to push 100% of the oil through a cooler with the temp of the oil somewhere below freezing temps. Stuff can break.
Try googling 'vernatherm for Lycoming' for more info.
That's because there ISN'T any promising alternative. Lots of really foolish ones, though.. I have a fairly jaded view of what I see a the grim reluctance of a large sector of the aviation (internal combustion engine) world, to move toward promising alternatives.
I live in California and we can not get any ethanol free gas so I have to use our 91 octane mogas with no problems in the 912 S. Have flown into Death Valley at - 280' making really low density altitude with no issues. I use auto fuel hoses that are formulated to withstand the ethanol and no problems. And after 18 yrs of flying the 912, no issues with carb rubber parts either.Terrific information Bob - I have been flying Rotax 912ULS for about 12 years - so far great reliability, economy, smooth, quiet (relatively) and performance.
To minimise any need to use AvGas, on an away trip, I carry two 20L collapsible fuel bladders, so that I can get ULP off field - system works well and there is usually a friendly business/private individual who will lend or transport me to the nearest reliable source of 95-98 RON.
For personal piece of mind, I do a 50 hr oil change (no filter) using AiroShell Sport plus 4 - no science behind this but I do hope I am enhancing my engines longevity.
Here in Canada, and I suspect in Alaska, multigrades are by far the preferred oils. Ambient temperature ranges are wide, and multigrades make sure that the engine pump can suck the stuff up out of the sump when cold, and still keep the moving stuff apart when hot.You can be a doubter, but doubt has little influence on the aviation world's reality. Lycoming and Continental aviation oils, are mostly single-weight, and even the multiweight oils are being run in engines that were designed to run single-weight. Lyc oils are typically 50 weight.
But would you disable the Vernatherm in a Lyc?
This one makes it a bit clearer:
Well I do have my PPL - trained in & flew mainly Cessna's (from straight tails to CSR) for a few years, before discovering Recreational Aviation Australia (RAA) and the delights of Rotax 912ULS in an ATEC Zephyr. RAA allow you to do all your own maintenance, in non commercial use aircraft, subject to passing a proficiency test. Now have a, yet to fly, Sonex/Rotax 912ULS (registered RAA). In preparation for the Sonex, recently did my tail wheel endorsement in a Citabria.I suggest that I was the 1st person to respond, in that specific thread you mention. I again ask, what's your experience with 'traditional' aircraft engines and their operation? I would think that if you had experience with them, you'd have some understanding of 'why owner/mechanics are sticking with such ancient oil technology'. A 9 series Rotax is *not* the same animal as a 'traditional' a/c engine, nor is it subject to the same rules/regulations/real world operating limitations.
That is one of the problems with internet forums, including HBA. To benefit from this one, the reader must learn to distinguish fact from opinion. As Orion frequently wrote, “What one believes is irrelevant in science.”So many differing opinions but just the one topic - crankcase oil.
It may not be “traditional”, but, even though I don’t like it, it has dominated the sport aviation world market for decades.True the Rotax 9's are not "traditional a/c engines" - my opinion, clearly the better future, especially with the development of fuel injected variants.
Oh perceptive BJC , I would encourage you to ask; why is this so?It may not be “traditional”, but, even though I don’t like it, it has dominated the sport aviation world market for decades.
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